STOPPING LEAKY & CORRODED CONCRETE TANKS
Despite 100 years of research and the release of various design standards, storage tank failures still exist. Codes committees, particularly ACI350, work hard to address this to the best of their ability but consultants and contractors often find the devil is in the detail. Several contributing factors can lead to a leaky tank from improper design, construction, and maintenance.
There are several technologies to consider when designing a storage tank. Coating solutions such as polyurethane and epoxy are widely used but require significant ongoing maintenance and have limitations in more aggressive environments (especially when exposed H2S). HDPE, fiberglass, and glass-lined steel will provide good service life, but all prove costly. So, where can you find a tank technology that’s fail-safe and will not only outperform conventional methods but extends service life?
COMBINING A WATERTIGHT LINER WITH STAY-IN-PLACE FORMWORK
For decades, engineers and owners have been looking for a way to improve the performance of tanks without increasing costs so dramatically, as is the delta between polyurethane-coated concrete tanks and most other systems (ie; glass-lined steel, fiberglass, or HDPE welded liners).
In 1997 Octaform began constructing liquid containment tanks using its proven PVC stay-in-place formwork system. These original tanks were built for manure containment in the agricultural sector, with applications in worldwide aquaculture soon following. The stretching of the PVC panels during the concrete pour resulted in a watertight wall. These tanks have performed for over twenty years, in temperatures ranging from -35ºC to 35ºC.
Due to the obvious advantages of zero maintenance and extended service life of these tanks, Octaform soon became widely recognized for a variety of tank applications. Consultants and owners embraced Octaform for diverse liquid containment applications, including on-land aquaculture, and biogas. The PVC-PVC joint and the concrete were the only barriers to leakage, prompting Octaform to apply its creative, innovative principles to engineer a more robust and secure solution.
INTRODUCING SNAP LOCK TIGHT. A COMPLETELY SEALED WALL SURFACE
Although there were already field-proven tanks that had successfully contained digestate, H2S for over two decades with no corrosion or leakage, likely due to the tight seams, Octaform wanted to improve on the design and offer something that would guarantee leak protection even in the face of inconsistencies in concrete execution.
“We now see consultants and owners embracing Octaform not only to apply some value engineering and reduce costs but because they have the assurance that the SLT liner means a minor rock-pocket or cold joint won’t mean a leaky tank, they have that extra assurance.”
- James Carter, Water Wastewater Solutions Lead, Octaform
Octaform modified and improved its system through the introduction of our patented SnapLockTight™ (SLT™) panel. SLT™ was originally designed for the containment of clear liquids and was subsequently modified to meet the demands of the emerging biogas industry. The objective was to develop a liquid and gas-tight wall system for biogas applications, including the containment of corrosive liquids and pressurized gas.
The panel is co-extruded with an anti-microbial bead which acts as a gasket and provides a watertight finish which also inhibits mold growth. The unique joint provides a proven seal that requires no re-coating and will last the life of your tank. Lab results on the SLT panel confirm that it will retain water over 68 PSI or 140′ of head pressure.
Additionally, leaving a watertight form on the concrete permanently, improves concrete hardness and curing, even further reducing the risk of leakage from cracking or capillarization. Testing on Octaform tanks consistently provides results that show up to 40% increased hardness to concrete formed with traditional methods.
The built-in PVC finish will protect your tank walls from corrosion, cracks, and leaks. It virtually eliminates the need for regular maintenance, no need to expect downtime for repairs or re-application of sealants and coatings.
In addition to assurance of the seal, many contractors have seen solutions inconsistently deployed in the field. Octaform designed SLT to literally “Snap-Locked” meaning it is either connected and sealed or not, there are no half-measures or risk of a poorly connected panel. It is virtually impossible to half-close a panel due to the shaping of the interface and the snapping sound that occurs.
Octaform’s estimating, construction support and assurance teams will be present from design to installation, with every project we recommend pre-specification and pre-construction meetings with your Octaform representative to ensure all bases are covered from a technical standpoint. In preparation for the arrival of the components, one of our field technicians will host a training session with your contractor for a detailed overview of the construction process.
Contractors and owners are pleasantly surprised the first time they install Octaform. With our “At-Your-Side™” approach that starts at estimating and goes through pre-construction, and on-site phases for bracing, formwork assembly, and re-bar placement, we take full ownership of ensuring your success. Octaform is supported worldwide and because of this, is commonly installed by contractors that have never used the system before, and is designed to ensure the first job is hassle-free, on-time, and on-budget.
With the introduction of SLT™, it is near impossible to assemble your tank wall without full joint closures in the interior. The SLT™ slides easily into the connector channels to engage the locking mechanism and close the seal. This provides a very satisfying ‘click’ once closed.
The nature of the wall assembly makes on-site inspection easy. The exterior panels can be lifted at any point for inspection of the rebar placement and tying. Our representatives will assist with an on-site inspection and detailed reporting, to ensure your tank is set-up for decades of reliability.
- 68 PSI 140’ head pressure liner
- NSF Potable water certified
- Improved concrete performance, reduced cracking and water ingress
- Resistant to corrosion from H2S, chloride contamination, etc.
- Reduced risk of leaks even in presence of minor cold joints or rock-pockets
Some opportunities to value-engineer mix design and re-bar density to reduce or meet overall cost versus bare concrete with the added assurance of a 140’ head pressure tested liner.